GROWTH AND NOCTURNAL ACID ACCUMULATION DURING EARLY ONTOGENY OF AGAVEATTENUATA GROWN IN NUTRIENT SOLUTION AND IN-VITRO CULTURE

Dry matter production of shoots and roots and the diurnal fluctuation of titratable acidity of single leaves were investigated in the CAM pl ant Agave attenuata during the first 70 d after germination. The plant s were grown either in vermiculite sub-irrigated with a nutrient solut ion or in in vitro cultures on an inorganic nutrient agar. Two types o f culture tube covers were used: either airtight closures or polypropy lene caps with membranes permeable to air. In the earliest ontogenetic phases of development (cotyledon and primary leaf stage), the plants were already able to carry out considerable nocturnal organic acid acc umulation. In vitro cultivated plants, from the beginning of their dev elopment, were also capable of diurnal acid fluctuation, though of dis tinctly weaker activity than the pot plants. The mean relative growth rates (RGR) of pot culture plantlets approached a third of perennial h erbaceous plants. Plantlets grown in in vitro culture reached only hal f to the one quarter of the RGR of pot plants. The reduced yield could be attributed to the low CO2 supply in the culture tubes and the less than optimal water and nutrient supply in the agar medium.